Which is better for a DBA (Swarm); powered subs or unpowered?

@audiokinesis 

Duke,
Glad you joined! Would the ability to time-adjust each of the 4 subs improve sound? Like Toole described in his Sound Reproduction?

I've gone from 1 Rel to two sealed DIY 12" Rythmiks in a digitally active 4-way stereo system, where the subs play mono. I'm thinking of adding two more Rythmiks, which have a number of adjustments from the plate amp including phase. I was wondering if the addition of a box receiving the summed mono subs signal and adjusting time on each would further improve things vs "just" adjusting phase on each. 

Regards

@audiokinesis 

"My recollection is that Toole was referring to a Harmon subwoofer integrator processor which optimized the gain, frequency response, lowpass filter, phase, delay, and equalization based on in-room measurements. I assume it does what they claim."  

Duke, thanks for the answer. I think Toole was referring to an integrator, but I don't know it was the integrator process. On chapter 13 "Making (bass) waves - below the transition frequency" he shows several examples where 4 subs are used in a rectangular room and optimized (through an optimizator) to minimize seat to seat SPL variation at 5 seating positions. The optimizator adjusts overall level (dB), delay (ms), and EQ at a given point (frequency, Q, level). It's not clear to me if said delay was introduced through DSP or just a "phase" adjustment.

I can measure with REW and optimize with MSO for example, but if actual delays are needed then I would need a digital processor to incorporate these.